Inflammatory, Idiopathic, Immune MediatedNeoplastic Diseases

Cards (29)

  • Myositis (Inflammatory Diseases of Muscle)
  • Types of myositis
    • Bacterial
    • Parasitic
    • Immune mediated
    • Viral
    • Idiopathic
  • Black Leg (Clostridial myositis)
    Acute fatal emphysematous myositis caused by Clostridium chauvoei
  • Pathogenesis of Black Leg
    1. Soil-containing spores > ingestion > GIT/liver > spores in muscle (latent)
    2. Muscle injury/hemorrhage > change in local environment (O2 tension, pH, etc.) > germination of spores in the muscle > exotoxins > edema, myonecrosis > emphysema > generalized toxaemia > death (.24 hours)
  • Gross Pathology of Black Leg
    • Affects large muscle masses such as those of the pectoral, pelvic, crural and scapular regions
    • Occasionally involves the musculature of the tongue, heart or diaphragm
    • Dark discoloration of the musculature and subcutaneous tissue
  • Black Leg
    • Affected muscles are black, with gas (emphysema) and crepitate on palpation
    • Rancid (butter) odor in affected tissues
    • Mild interstitial and subcutaneous edema (gelatinous fluid) peripherally to the lesion
    • Fibrin tags on the epicardial and pleural surfaces
    • Diffuse serosal hemorrhages, an early bloat and severe pulmonary edema
  • Histopathology of Black Leg
    • Muscle fibers are moderately hypereosinophilic
    • Blood vessels are engorged with blood
    • Interstitium is distended with fluid and many leukocytes
  • Fluorescent Antibody Test (FA test)
    Confirmatory test for Clostridium chauvoei
  • Malignant Edema (Gas Gangrene)
    Acute fatal infection caused by Clostridium septicum, Cl. perfringens, Cl. novyi, Cl. sordelli and Cl. Chauvoei
  • Malignant Edema (Gas Gangrene)

    • Generally affects ruminants, horses and swine
    • Route of entry is always through a wound
    • Spores are commonly present in soil and feces
    • Affected areas are cold on palpation and crepitous
    • Generalized signs of toxemia, and finally prostration death
    • Severe edematous and to a lesser extent emphysematous expansion of the subcutaneous connective tissues
    • Hemorrhage
    • Skin remains generally intact
  • Parasitic Myositis
    • Trichinosis: Trichinella spiralis
    • Cysticercosis: Cysticercus bovis, Cyticerucus cellulosae, Cysticerucs ovis
    • Sarcocystis
    • Neospora
    • Toxoplasma
  • Cysticercosis
    Indirect cycle: Tapeworm in definitive host, Cysticercus (cyst with larvae) in intermediate host (muscle)
  • Cysticercosis
    • Cysticerci are large visible cysts (1-2 cm) filled with clear fluid and one single parasitic larvae
    • Cysticerci can also parasitize the brain (neurocysticercosis)
  • Trichinella spiralis
    • Zoonotic parasitic disease acquired through consumption of poorly cooked meat
    • Adult parasite lives in the small intestine, larvae migrate from the intestine to tissues, with some predilection for muscles of tongue, masseter, diaphragm intercostal and eye
  • Trichinella spiralis
    • Larvae become encysted in the muscle
    • Larvae induce only minimal host response, difficult to see them grossly without a trichinoscope
  • Sarcocystosis (Sarcosporidiosis)

    • Protozoal disease affecting primarily herbivorous and pigs
    • Indirect life-cycle where carnivores are definitive hosts and herbivores, and pigs, birds are the intermediate hosts
  • Sarcocystis are so common that most herbivorous have parasites in their musculature and there is no inflammatory response
  • Sarcocystis
    • Parasitic cyst filled with hundreds of bradyzoites
    • Cysts may become grossly visible as white nodules, especially in sheep and wild birds
  • Eosinophilic Myositis

    Condition associated with Sarcocystis, of no real clinical significance, seen sporadically in the meat in cattle and sheep
  • Eosinophilic Myositis
    • Appears grossly as focal or locally extensive, well-demarcated areas of green discoloration in the muscle
    • Microscopic examination reveals muscle degeneration and infiltrates of eosinophils
  • Masticatory Muscle Myositis (MMM)
    Rare and acute (relapsing) eosinophilic myositis in dogs characterized by swollen painful jaws, and blood eosinophilia
  • Masticatory Muscle Myositis (MMM)
    • Pathogenesis involves auto-antibodies against a particular protein present in fibers IIM (unique fiber in masticatory muscles)
    • Lesions are typically bilateral
    • In acute cases there is edema and extensive infiltration of eosinophils in the masseter, temporal, pterygoid muscles
    • In the chronic form, the cellular infiltrates change to lymphocytes and plasma cells and the fibers become atrophic
  • Myasthenia Gravis
    • Rare neuromuscular junction disease in dogs, cats and humans
    • Caused by reduced number of acetylcholine receptors (hereditary) or antibodies against acetylcholine receptors (acquired)
  • Myasthenia Gravis
    • Clinical signs: Weakness, fatigue, dysphagia
    • No significant changes in muscle, but megaesophagus in dogs leading to aspiration pneumonia
  • Tumors of Muscle
    • Spontaneous tumors of striated muscles are rare in veterinary medicine but common in experimental pathology (toxicology)
    • Neoplasia arising in muscle may include tumors from striated muscle, adipose cells, fibrous connective tissue, nerves or vascular cells
  • Rhabdomyoma
    Benign tumor, most common in cattle, sheep and pigs, generally congenital, common in the heart
  • Rhabdomyosarcoma
    Malignant tumor, seen in cattle, sheep, dog and horses, large poorly encapsulated nodules, prone to metastasis
  • Rhabdomyosarcoma
    • Neoplastic cells are characterized by poor parallel alignment, the presence of striation, and anisokaryotic, slightly pleomorphic nuclei
  • Liposarcoma
    Malignant, invasive tumor of adipose cells, rarely seen in animals